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Didymocyrtis antepenultima (Riedel and Sanfilippo, 1970)

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Cortical and medullary shell similar to those of Cannartus laticonus and Ommatartus penultimus. C. laticonus has no polar caps (the distal boundary of the narrow clearer zone between the cortical twinshell and spongy column is parallel to the distal wall of the cortical shell, as in pl. 14, fig. 2), while O. penultimus s.s. has caps at least as well developed as its holotype (Riedel, 1957, Pl. 1, fig. 1). O. antepenultimus includes all forms in which the development of the caps (and spongy columns) is intermediate between these two.
Length of spongy columns 20-90µ; their median breadth 20-55µ. Height of polar caps 15-35µ. Length of cortical shell 90-115µ; its maximum breadth (including protuberances) 75-115µ. Breadth of outer medullary shell 25-40µ. (Measurements based on specimens from AMPH 6P,15-17cm; SDSE 87, 399-400cm; and PROA 102P, 490-492cm.)
(Riedel and Sanfilippo) 1970











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